This invention relates to an adhesion enhancing coating and coated paper for pressure fixed toner particles, and more particularly to a coating and coated paper for use in ion deposition printing applications which provides improved adhesion of the toner particles to the printed product produced.
Business forms, labels, bar codes, and security documents are printed on a wide variety of commercial printing devices. Traditional mechanical impact printers have been used in the past for many of these applications, especially in the imprinting of information on security documents such as checks. The mechanical impact produced by the printers, whether based on formed characters or dot matrix, generally provides information which adheres quite well to the underlying paper document. However, such mechanical impact printers have limited speed, high noise levels, and high costs for parts and maintenance.
With the advance of microcomputer technology, a number of faster printing methods have been developed to take advantage of the high-speed printing output which is now possible. Recently developed nonimpact printers are fast, quiet, and potentially more reliable because of fewer moving parts. Ion deposition printers are one class of these newer nonimpact printers. Such printers operate by directing a computer-controlled stream of ions in a specific pattern onto an image cylinder or drum to form a latent image.
As the image cylinder is rotated, toner particles from a toner cartridge are deposited on the image areas on the cylinder and held there by the charged ions. As the image cylinder continues to rotate, the now visible toner image on the cylinder is then transferred to a paper web which has the correct level of conductivity required. Typically, a solid roller is positioned opposite the image cylinder and exerts pressure on the toner and web to simultaneously transfer and fix the toner to the web.
Descriptions of noncontact printers such as ion deposition printers, the toners used therein, and the papers used for printing on them are known. See, for example, "The evolution of Toning Technology: Past, Present, and Future", Fourth Annual Guide to Ribbons and Toner, Product Overview and Industry Directory published by Datek Information Services, Inc.(1983); "New Papers for New Printers", Chemtech (1986); and "A review of Dry and Liquid Toner Technology", The 1988 Datek Imaging Supplies Manual, all of the disclosures of which are hereby incorporated by reference.
While ion deposition printing is fast and quiet, the process has had significant limitations which have prevented its wide use in printing certain types of documents such as checks, other security documents, labels, and documents having bar code information thereon. These limitations include the inability to achieve satisfactory toner bonding on a large variety of paper products used to make such documents. For example, documents such as checks which contain not only payee and amount information but also MICR coding for automated handling must be able to withstand multiple handling and sorting cycles in high speed automated machinery. If the toner containing information such as MICR or bar coding on the document flakes off or is otherwise removed during such operations, the document will be rejected from the system and will have to be handled manually.
Additionally, because of the lack of strong adherence of toner to paper, documents printed using ion deposition printers are subject to deliberate alteration by counterfeiters, forgers, and the like. For example, check amounts and/or payee information may be readily scraped off and new amounts substituted by the unscrupulous. While it may be possible to employ additional heat fusing steps to adhere the toner particles to paper as the information is printed, this adds an additional stage to the printing process, and care must be taken not to overheat or melt the toner particles or scorch the paper stock.
Still further, papers used in ion deposition printing systems must have a very narrow range of volume and surface resistivities to insure that the toner image is properly transferred from the image cylinder or drum. Such papers are also required to have a relatively high degree of surface smoothness and flatness, a specific range of moisture contents, and resistance to curl. Fabrication of special papers to have these characteristics increases the costs of such papers and their use.
Accordingly, there remains a need in the art for a paper product which provides enhanced toner adhesion for noncontact printed products without the drawbacks of prior art products.